Method and apparatus for the disinfection of liquids by anodic oxidation and preceding reduction

ABSTRACT

This invention relates to the disinfection of liquids, preferably of water-containing liquids by anodic oxidation. The disinfecting effect of anodic oxidation in an electrolytic cell is known. This invention is directed to the improvement of the disinfecting effect while maintaining the investment for the apparatus at a minimum and avoiding the addition of disinfecting additives.

United States Patent Eibl et al.

METHOD AND APPARATUS FOR THE DISINFECTION OF LIQUIDS BY ANODIC OXIDATIONAND PRECEDING REDUCTION lnventors: Volker Eibl; August Reis, both ofMunich, Germany Sachs-Systemtechnik Gmbl-l, Schweinfurt, Germany Filed:May 28, 1974' Appl. No.: 473,377

Assignee:

Foreign Application Priority Data June 9, 1973 Germany 2329630 US. Cl.204/151; 204/130; 204/149 Int. Cl. C0213 1/82 Field of Search 204/149,151, 130, 180 P References Cited UNITED STATES PATENTS 10/1926 Speed204/151 X [4 Oct. 7, 1975 2,882,210 4/1959 Jenks 204/151 3,135,6746/1964 Ruetschi ..204/151 Primary Examiner-John l-l. Mack AssistantExaminer-A. C. Prescott Attorney, Agent, or Firm-Hans Berman [57]ABSTRACT 3 Claims, 1 Drawing Figure METHOD AND APPARATUS FOR THEDISINFECTION OF LIQUIDS BY ANODIC OXIDATION AND PRECEDING REDUCTION Thisinvention is directed to a method of disinfecting liquids, preferablywater-containing liquids, by anodic oxidation, wherein the liquid to bedisinfected is exposed in a first electrolytic cell having a cathode andan anode within the anode compartment to an electric current, cathodecompartment and anode compartment being separated by a diaphragm.

This method consists in exposing the liquid to be disinfected to areducing agent before the treatment in the electrolytic cell, i.e.,enriching the liquid to be disinfected with electrons.

By this measure the disinfecting effect in the anodic oxidation isessentially improved, so that the size of the apparatus and therewithconstruction expenses are reduced; furthermore there is achieved theadvantage that the liquid to be disinfected stays in the apparatus for ashorter time, which guarantees a reduction of separations of theelectrode material and thus a disinfecting effect which is substantiallyfree of negative results.

The method according to this invention is especially simply to realizeif the cathode compartment of an electrolytic cell is used as thereduction agent. In this event it is not necessary to add any reagentsto the liquid so as to obtain a reduction effect. In this connection itis of some advantage to make such an arrangement that a plurality ofelectrolytic cells are passed subsequently, whereby the liquid flowsthrough the cathode compartment of the first cell and through the anodecompartments of the following cells.

Furthermore, this invention relates to an apparatus for performing theafore-mentioned method. Such apparatus comprises a plurality ofelectrolytic cells arranged in series, each electrolytic cell beingprovided with a cathode compartment and an anode compartment, at leastone of said cells being provided with an inlet and an outlet in itscathode compartment, the rest of the electrolytic cell being providedwith respective inlets and outlets in their anode compartment, the cellsbeing arranged in series such that the outlet from the cathodecompartment of said one cell is connected to the inlet of the anodecompartment of another cell, possible further cells being connected withthe inlet of their anode compartment to the outlet of the anodecompartment of the preceding cell and with their outlet to the inlet ofthe anode compartment of the subsequent cell. This allows a very simpleconstruction having substantially identical parts and saving space.

Other features and many of the attendant advantages of this inventionwill readily be understood from the following detailed description of apreferred embodiment when considered in connection with the appendeddrawing:

In the embodiment as shown in the drawing there are arranged in seriesthree electrolytic cells. The principle arrangement is such that theliquid to be disinfected passes through the cathode compartment 6 of thefirst cell and through the anode compartment 7 of the two followingcells. All the three cells are marked by identic reference numerals,because they may be identic in their construction; only theirarrangement with respect to each other is modified according to thisinvention. In each of the three cells illustrated, the space in acontainer 1 is divided into two compartments 6, 7 by a diaphragm 8. Theliquid to be purified is fed to the compartment 6 of the first cellthrough an inlet duct 9, caused to flow from the compartment 6 of thefirst cell to the compartment 7 of the second cell through a connectingline 10. It enters the compartment 7 of the third cell from thecompartment 7 of the second cell through a connecting line 11, and isdischarged from the compartment 7 of the third cell through an outletduct 12.

Each compartment 6 contains an electrode 4 connected by a conductor 5 tothe negative pole of a source of electric current. Each compartment 7contains an electrode 2 connected to the positive pole of the currentsource by a conductor 3. During operation of the apparatus, liquid flowssequentially through respective compartments of the first, second, andthird cells whose electrodes are made the cathode in the first cell andthe anode in the second and third cells.

The basic function of the apparatus is that before the very anodicoxidation there takes place a reduction process in the cathodecompartment 6 of the first electrolytic cell for the purpose ofdisinfection within the anode compartments 7 of the second and the thirdelectrolytic cell. The effect of the anodic oxidation turned out to havebeen improved in this way, in particular there is a more rapid cut-downof number of germs within a relatively short period.

A comparison of the apparatus according to this in vention on the onehand with the system of a simple liquid flow through the anodecompartment of an electrolytic cell on the other hand has shownessential advantages achieved by this invention. Starting from a numberof 10 coli germs per milliliter and having a current intensity in theelectrolytic cell of approximately to 200 mA at a voltage between theanode plate 2 and the cathode plate 4 of approximately 10 to 20 V, thecirculation test (this means the duct 12 is connected with duct 9 by apump to form a closed circulation), in particular up to a duration offour minutes, results in a considerably greater cut-down of the numberof germs when employing the method according to this invention. Thediaphragma may be of any known material. The tests as made up to nowhave not brought more favourable results from the employment of onlycationpermeable diaphragms or only anionpermeable diaphragmsrespectively. By the employment of the method of this invention, thecirculation test resulted after approximately 4 to 6 minutes in totaldisinfection, whereas according to the prior art method there was nocut-down of the concentration of germs after a certain time.

The expression disinfection as used in the specification and in theclaims is to comprise also decontammination and detoxication.

We claim:

1. A method of purifying an aqueous liquid contaminated withmicroorganisms which comprises:

a. causing said liquid to flow sequentially through respective firstcompartments of a first electrolytic cell and of a second electrolyticcell, each cell having a first compartment and a second compartmentseparated from said first compartment by a permeable diaphragm, eachcell further having a first electrode in said first compartment thereofand a second electrode in said second compartment thereof;

b. passing direct electric current through said liquid in said firstcell between the first electrode of said cell, said third cell having anelectrode in each of said two compartments, said two compartments beingseparated by a permeable diaphragm, electric current being passedthrough said liquid in said third cell between the electrode in said onecompartment as the anode and the electrode in the other compartment asthe cathode.

3. A method as set forth in claim 1, wherein said liquid, after beingwithdrawn from said second cell, is re turned to the first compartmentof said first cell.

1. A METHOD OF PURIFYING AN AQUEOUS LIQUID CONTAMINATED WITHMICROORGANISMS WHICH COMPRIES: A. CAUSING SAID LIQUID TO FLOWSEQUENTIALLY THROUGH RESPECTIVE FIRST COMPARTMENTS OF A FIRSTELECTROLYTIC CELL AND OF A SECOND ELECTROLYTIC CELL, EACH CELL HAVING AFIRST COMPARTMENT AND A SECOND COMPARTMENT SEPARATED FROM SAID FIRSTCOMPARTMENT BY A PERMEABLE DIAPHRAGM, EACH CELL FURTHER HAVING A FIRSTELECTRODE IN SAID FIRST COMPARTMENT THEREOF AND A SECOND ELECTRODE INSAID SECOND COMPARTMENT THEREOF: B. PASSING DIRECT ELECTRIC CURRENTTHROUGH SAID LIQUID IN SAID FIRST CELL BETWEEN THE FIRST ELECTRODE OFSAID FIRST CELL AS THE CATHODE AND THE SECOND ELECTRODE OF SAID FIRSTCELL AS THE ANODE: C. PASSING DIRECT ELECTRIC CURRENT THROUGH SAIDLIQUID IN SAID SECOND CELL BETWEEN THE FIRST ELECTRODE OF SAID SECONDCELL AS THE ANODE AND THE SECOND ELECTRODE OF SAID SECOND CELL AS THECATHODE: AND D. WITHDRAWING THE LIQUID IN PURIFIED CONDITION FROM THEFIRST COMPARTMENT OF SAID SECOND CELL.
 2. A method as set forth in claim1, wherein said liquid, after being withdrawn from said second cell, ispassed through one of two compartments of a third cell, said third cellhaving an electrode in each of said two compartments, said twocompartments being separated by a permeable diaphragm, electric currentbeing passed through said liquid in said third cell between theelectrode in said one compartment as the anode and the electrode in theother compartment as the cathode.
 3. A method as set forth in claim 1,wherein said liquid, after being withdrawn from said second cell, isreturned to the first compartment of said first cell.